SB 



Issued January 21, 1918. 

U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 272. 

B. T. GALLOWAY, Chief of Bureau. 



HEREDITY OF A MAIZE VARIATION. 



G. N. COLLINS, 
Botanist, Crop Acclimatization and Adaptation Investigations, 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1913. 



i^"Mt«fe>. 




Book. 1V\?T'7(^ 



'/ 



3fl f 



-^ 



^^ 



Issued January 2], 1313. 

U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF PUNT INDUSTRY— BULLETIN NO. 272. ' ;' / 



E. T. GALLOWAY. Ckicf of Bureau. 



Ce U- i 






HEREDITY OF A MAIZE VARIATION. 



G. N. COLLINS, 
Botanist, Crop Acdvaatization and Adaptation Investigations. 




WASHINGTON: 

GOV-EBNMENT PBINTINO OmOE. 
1913. 









BUREAU OF PLANT INDUSTRY. 



Chief of Bureau, Beverly T. Galloway. 
Assistant Chief of Bureau, Wellum A. Taylor. 
Editor, 3. E. Rockwell. 
Chief Cleric, James E. Jon'e.-*. 



Crop Acclimat!z.vtuin and Adaptation Investigations. 

scientific staff. 

O. F. Cook, Bioriomist in Charge. 

G. N. Collins, Botanist. 
H. Pittier, Special Field Agent. 

A. T, Anders, J. H. Kinsler, Argyle McLachian, and D. A. Saunders, Agents. 
C. H. Clark, C. B. Doyle, J. H. Kempton, and R. M. Meade, Assistants. 
272 
2 



D. OF D. 
lf\U 22 1913 



ci.y* (3"6>^ 



LEHER OF TRANSMITTAL. 



U. S. Department of Agriculture, 

Bureau of Plant Industry, 

Office of the Chief, 
WasJiington, D. C, October 4, 1912. 
Sm: I iiave the honor to transmit herewith a paper entitled 
"Heredity of a Maize Variation," by Mr. G. N. Collins, Botanist, 
Crop Acclimatization and Adaptation Investigations, and recommend 
its publication as Bulletin No. 272 of the series of this Bureau. 
Respectfully, 

Wm. a. Taylor, 
Acting Chief of Bureau . 
Hon. James Wilson, 

Secretary of Agriculture. 

272 3 



CONTENTS. 

Page. 

Introduction 7 

Endospenn color in maize 7 

Description of the mutation 9 

Progeny of the albinistic ear 10 

First xenia generation 10 

Second xenia generation 10 

Third xenia generation 13 

Progeny of ear No. 741 13 

Progeny of ear No. 721 16 

Cross of the albinistic ear with a White Dent variety 17 

First generation 17 

Second generation 18 

Cross of the albinistic ear with the Hopi variety 20 

Discussion of results -. 21 

Conclusions 22 

272 5 



ILLUSTRATIONS. 



PLATE. 

Page. 

Plate I. Fig. 1. — A representative ear of Gorham Yellow Dent com. Fig. 2. — 

An albinistic mutation from Gorham Yellow Dent com . . 8 

TEXT FIGURE. 

Fig. 1. Diagram showing the inheritance of endosperm color in tlie progeny of 

an albinistic ear of corn 11 

27-2 
6 



B. P. I.— 789. 



HEREDITY OF A MAIZE VARIATION. 



INTRODUCTION. 

A single white ear of maize was discovered in a strain of uniformly 
yellow corn. The conditions under which the ear appeared and 
the behavior of its progen}^ both indicated that its occurrence was 
in the nature of a direct mutation and not the result of an accidental 
mixture of seed. The present paper is an account of the heredity 
of this albinistic ear. 

Albinistic mutations are not uncommon in both plants and animals, 
and many white varieties are supposed to have originated in this 
way, but so far as known this is the first instance of a mutation of 
this kind affecting the endosperm of maize. The phenomenon is 
beUeved to be of interest, since it suggests one manner in which color 
diversity in maize may arise. 

In maize the endosperm or the starchy portion of the seed exists 
in two colors, yellow and white. Although this difference in the 
color of the endosperm or starch may in reality be unimportant, it is, 
nevertheless, the mark which in the minds of most corn growers 
distinguishes two great classes of corn. In the corn products pre- 
pared for human food the distinction between yellow and white is 
fundamental and affords a most striking example of the different 
customs of the North and the South. In the South the use of yellow 
varieties of corn for human food is almost unknown, while in the 
North, although white varieties are widely grown, food preparations 
are made almost entirely from yellow corn. 

ENDOSPERM COLOR IN MAIZE. 

The popular discrimination between white and yellow varieties 
of maize for human food is not the result of mere prejudice, for there 
can be no doubt regarding the difference in taste between the yeUow 
and the white preparations that are on the market. What is not 
clear is whether the color is necessaril}^ associated with the taste. 
The characteristic taste of yeUow meal, for example, may be due to 
the choice of varieties, and the color may be only incidental. 

In the endosperm of maize the yellow color when present is always 
confined to the corneous or hornj^ portion of the seed. So far as 
observed, the soft or starchy endosperm that occupies the center of 
the grain and which in flour varieties fiUs practically the entire seed 

• 272 7 



8 HEEEDITY OF A MAIZE VARIATION. 

is always white. The yellow color when present in seeds of a soft 
variety is therefore confined to the thin outer layer of the translucent 
or horny endosperm.^ This definite relation that exists between 
color and texture makes it appear not improbable that there may 
in reality be a similar relation between color and taste. 

Though the yellow and the white varieties are constantly being 
mixed, there is little tendency for the color to become intermediate. 
Very hght-yellow seeds are sometimes encountered as a result of 
xenia in varieties where the yellow is imperfectly dominant, but the 
endosperm of fixed varieties is either distinctly yellow or pure white. 

One source of slight variation in the intensity of the yellow color 
lies in the varying amount of the horny endosperm to which the 
yellow color is confined. Thus, in soft varieties, although the thin 
layer of horny endosperm may be as dark as in horny varieties, the 
layer is so thin that the general appearance of the seed is compara- 
tively light. 

Tracy ^ has shown that, as a rule, the white varieties are more 
productive than the yellow. His conclusions are based on averages 
of all the varieties regarding which data could be obtained, and here 
again it is not perfectly clear that the color bears any casual relation 
to the difference in productive power. So far as known, no careful 
comparisons have been made between the yellow and the white 
strains of the same variety. 

How maize came to be differentiated into yellow and white varie- 
ties is shrouded in the mystery that envelops the domestication of 
the plant. The only suggestion is that of Tracy ,^ who advances the 
idea that white varieties are in the nature of degenerations from the 
yellow. Both yellow and white varieties are common among the 
most primitive types of corn that are now being grown in the Ameri- 
can Tropics. The remams of prehistoric ears are usually so dis- 
integrated that it is impossible to tell whether the endosperm is 
yellow or white, but the writer recalls none which did not have either 
the pericarp or aleurone layer colored. 

The inheritance of the endosperm color in maize has been made 
the subject of comprehensive investigations from the Mendelian 
point of view. In the exhaustive experiments of East and Hayes * 
it was shown that in crosses between white and yellow strains the 
yellow color is dominant to the white in the first xenia generation, 

» Yellow may also occur in the waxy endosperm of the Chinese corn. See Bulletin 161, Bureau of Plant 
Industry, U. S. Dept. of Agriculture, entitled " A new type of Indian corn from China." 

2 Tracy, S. M. The relation of color to yield in corn. Presidential Address at the Thirty-First Annual 
Meeting of the Society for the Promotion of Agricultural Science. Washington, D. C, Nov. 15, 1910. 

» Op. cit., pp. 12-13. 

•• East, E. M. A Mendelian interpretation of variation that is apparently continuous. American 
Naturalist, vol. 44, February, 1910, pp. 65-82. 

East, E. M., and Hayes, H. K. Inheritance iu maize. Butbtin 107, Connecticut Agricultural Experi- 
ment Station, April, 1911. 
272 



Bui. 272, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



Plate I. 




-A Representative Ear of Gorham 
Yellow Dent Corn. 

(Natural .size.) 



Fig. 2.— An Albinistic Mutation 
FROM Gorham Yellow Dent 
Corn. 

(Natural size.) 



DESCRIPTION OF THE MUTATION. 9 

and that in the next generation the colors usually segregate in a 
3 to 1 ratio. In certain crosses reported by these authors, however, 
the segregation was in the ratio of 1 5 yellow seeds to 1 white, a ratio 
explainable on the assumption that there are two factors or ingred- 
ients, either one of which will produce the yellow color, and that the 
factors are independent in inheritance. 

DESCRIPTION OF THE MUTATION. 

During the corn harvest of 1909 Mr. John Gorham, of Waco, Tex., 
observed a single white ear of a yellow-dent strain which he had 
selected carefully for several years. This ear came to the attention 
of Mr. O. F. Cook, of the Bureau of Plant Industry, who appreciated 
the interest of such a variation. The possibility that it might repre- 
sent a mutation was recognized, and an investigation of the case was 
suggested. 

The possibility of chance admixture of seed of a white variety 
seemed to be excluded, not only by the fact that the variety in which 
the sport appeared had been carefully selected on the place where it 
was being grown for a number of years but by the fact that no simi- 
lar white variety was known in the neighborhood. Moreover, it 
appeared very strange that an all-white ear could develop in a field 
of yellow com. Unless the ear had been entirely self-poUinated 
there should have been some yellow seeds as a result of xenia. At 
the same time it was apparent from differences in the shape and size 
of the ear that the variation did not consist merely in the loss of 
endosperm color. The most striking difference in form was that the 
kernels were much shorter than those of the yellow ears. 

The Gorham Yellow Dent, the variety m which the mutation 
occurred, has been developed by Mr. Gorham with the assistance of 
Mr. D. A. Saunders. A representative ear of this variety is shown 
in Plate I, figm-e 1. The color of the seed in this variety is a rich, 
dark yellow. The variety, though not as uniform as some pedigree 
cultures, is as constant in its behavior as most commercial varieties. 
In the examination of the crops and in the selection of seed for six 
consecutive years no other color variations have been observed by 
either Mr. Gorham or Mr. Saunders. 

A reproduction of a photograph of the white ear is shown in Plate 
I, figure 2. The ear was fully matured and well filled. In the 
original variety the cob is red; in the mutation it is pure white. The 
seed of the mutation, except on the closest examination, would also 
be considered pure white, but when carefully examined a very faint 
trace of yellow can be found near the base of most of the seeds. The 
color is much lighter than any first-generation hybrid of white and 
yellow that has come under observation. 

66514°— Bjil. 272—13 2 



10 HEREDITY OF A MAIZE VAEIATION". 

It was thought that a recently acquired character, such as this 
colorless endosperm appeared to be, might lack the regularity in 
behavior that obtains with characters of longer standing and in 
which the expression tendencies have become mora firmly estab- 
lished. The results have shown that the character, while Mendeloid 
in its inheritance, is not subject to definite and complete segregation. 

PROGENY OF THE ALBINISTIC EAR. 
FIRST XENIA GENERATION. 

It appears probable that the plant which produced the original 
white ear received pollen from ordinary Gorham plants. If so, the 
seeds represented the first xenia generation of a cross between white 
and yellow in which the white was dominant or nearly so. So far as 
known, this is the first instance of this kind, the yellow endosperm 
usually being dominant to white. 

Owing, perhaps, to a difference in the time of flowering, the seed 
of the original ear might have been self-pollinated, but in that case 
the self-pollinated progeny of this ear should have been all white, 
whereas varying percentages in the progeny showed the full yellow 
of the Gorham variety, giving further evidence that the ear had 
been cross-polUnated. It seems more reasonable, however, to asso- 
ciate this reversal of dominance with the appearance of a mutation 
where abnormal conditions may be expected to prevail rather than 
to assume that this unusual behavior should occur as a coincidence 
in connection with a single stray grain that had found its way into 
the seed planted in 1907. That the failure of dominance was not 
varietal but was largely confined to the original mutation is shown 
by the complete dominance of the yellow color in much of the progeny. 

Seed from the original mutation was planted in 1910. One self- 
pollinated ear, No. 930, and two cross-pollinated cars, Nos. 741 and 
721, were secured. The seed of these ears represents the second 
xenia generation. 

SECOND XENIA GENERATION. 

The self-pollinated ear. No. 930, had both white and yellow seeds, 
but the presence of a faint-reddish pericarp color made classification 
rather difficult. The appearance of a pericarp color may also be 
associated with the mutative change, but in the presence of the full- 
yellow color of the original variety this character might easily escape 
detection. In 1911 two hand-pollinated ears were grown from the 
seed of ear No. 930. One was pure white; the other contained only 
a few seeds, all of which had yellow endosperm. 

Ear No. 741 was a cross between two plants, Nos. 82 and 47, from 
seed of the original ear. Ear No. 721 was the reciprocal of ear No. 

2T2 



PROGENY OF THE ALBINISTIC EAR. 



11 



741, that is, plant No. 47 was pollinated by plant No. 82. The 
progeny of plants Nos. 82 and 47 are shown diagrammatically in 
figure 1. In both ears the seeds fell naturally into two groups: 
Dark yellow, like the original Gorham variety, and white or very 
light yellow seeds. Among both the light and dark-yellow seeds 
were some with white caps. The white cap appears as a character 
independent of the color of the body of the seed, but it is difficult to 
distinguish in the very light-colored seeds and is here left out of 
consideration. 

Of the two classes of seeds the dark yellow was comparatively 
uniform, and the second group of light-colored seeds was more 







fXAflfT-Mi^e 



*3^yZH£H*"* 



Fig. 1.— Diagram showing the inheritance of endosperm color in the progeny of an albinistic ear 

of corn. 

variable. It was even possible further to divide the second group 
into white and light-yellow seeds with some degree of positiveness. 
Table I shows the number of seeds in the different classes. 



Table I. — Classification showing the number oj seeds by endosperm colors in the second 

xenia generation. 



Ear No. 


1 1 
Total num- 1 Dark-yellow Light-yellow 
ber of seeds. seeds. seeds. 


White 
seeds. 


721 


592 
515 


436 
327 


96 
103 


60 


741 


85 






Total 


1,107 


763 


199 


145 







Considering first the two obvious classes, dark-yellow as contrasted 
with the light-yellow and the white seeds, and comparmg their 
numbers with the 3 to 1 ratio of a monohybrid, the results are shown 
in Table II. 



272 



12 



HEREDITY OF A MAIZE VAEIATION. 



Table II. — Number of white seeds of the second xenia generation compared %mth the 

monohybrid ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 
white seeds. 


Expected 
number of 
white seeds 
on a 3 to 1 
ratio. 


Deviation 
from ex- 
pected 
number of 
white seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 

of white 

seeds. 


721 


592 
515 


156 

188 


148±7.1 
129±6.6 


+ 8 
+59 


1.1 

8.9 


26.3 


741 


36.5 






Total 


1,107 


344 


277±10 


+67 


6.7 


31.1 







Ear No. 721 agrees as well as could be expected with the monohy- 
brid ratio. The reciprocal ear, No. 741, approaches more nearly the 
7 to 9 ratio of a dihybrid, but from this ratio it deviates nearly five 
times the probable error. It is not uncommon for reciprocals to 
differ in endosperm color, the female parent usually exerting the 
greater influence. This prepotency of the female usually shows 
itself, however, in the intensity of the color and not, as here, in dif- 
ferent numerical relations. No differences in the intensity of the 
color of the two ears were apparent. 

This deviation from the normal 3 to 1 ratio is the more interesting, 
since the progeny of the heterozygous seeds from both these ears, 
which are later discussed, exhibit the same classes of dark and light 
yellow or white seeds, and in nearly every ear the numbers are in the 
ratio of 3 to 1. 

Regarding the less ob\'ious distinction between the pure-white 
and light-yellow seeds in these ears, it will be seen that ear No. 721 
had 10.1 per cent and ear No. 741 had 16.5 per cent of the total num- 
ber of seeds classed as pure white. In neither case can the ratio be 
referred to either the monohj^brid or dihybrid ratios, which are 25 
per cent and 6.25 per cent, respectively. The numbers would be 
approximated if we assume that one of the parent plants was hetero- 
zygous for both of two factors, either one of which would produce 
yellow, and that the other parent possessed only one of these factors. 
The expected percentage of white seeds would then be 7 to 1, or 12.5 
per cent. Considered from this viewpoint the observed number shows 
the approximations given in Table III. 

Table III. — Number of pure-white seeds of the second xenia generation compared with 

a7 to ] ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 
pure-white 

seeds. 


Expected 
number of 
white seeds 
on a 7 to 1 
ratio. 


Deviation 

from 

expected 

number of 

white seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 
of white 

seeds. 


721 


592 
515 


60 
85 


74±5.4 
64±5.1 


-14 
+21 


2.6 
4.1 


10.1 


741 

Total 


16.5 


1,107 


145 


138±7.4 


+ 7 


.9 


13.1 



272 



PROGENY OF THE ALBINISTIC EAR. 13 

It should be remarked, in connection with the excess of white seeds 
in ear No. 741, that out of 14 self-pollinated ears grown from the white 
seeds of this ear the following season 2 showed light-yellow seeds. 
If this ratio held, and approximately 2 out of every 14 of the eai's 
classed as white are in reality very light yellow, the number of pure- 
white seeds would be reduced to 73, a deviation from the expected 
number of 9, or only 1.8 times the probable error. 

THIRD XENIA GENERATION. 

In the following year, 1911, 84 self-pollinated ears were secured 
from seed of the 2 reciprocal ears, Nos. 721 and 741. Sixty-four of 
these self-pollinated ears were from colored seeds. From the ratios 
secured in the second xenia generation it was suggested that one of 
the parents of these two ears might be heterozygous for one yellow 
factor, with the other factor absent, while the other parent was 
heterozygous for both factors. If this were true, the self-pollinated 
ears raised from the yellow seeds should have been colored as follows: 
Eighteen all yellow, 27 with 25 per cent of white seeds, and 18 with 
6.25 per cent of white seeds. 

In reality 15 ears were found with the seeds all yellow, 30 ears with 
approximately 25 per cent of white seeds. 4 ears that approximated 
6.25 per cent of white seeds, and 15 ears in which the classes w^ere 
either poorly marked or the number of white seeds were not referable 
to any expected ratio. Thus, the number of ears that were all yellow 
and those that had 25 per cent of the seeds white are seen to be in 
close accord with the expected ratios. 

While in most cases the distinction between the white and yellow 
seeds was perfectly obvious, it did not require close scrutmy to see 
that the seeds placed in the white class were not uniformly pure white. 
This phenomenon is further discussed when the details of the different 
ears are given. 

PROGENY OF EAR NO. 741. 

Ear No. 741, which resulted from crossing 2 plants from seed of 
the original albinistic ear, had 515 seeds that were classified as white, 
light yellow, and dark yellow. . Each class was planted separately in 
1911. 

White seeds. — Fourteen self-pollinated ears from the white seeds of 
No. 741 gave 12 pure-white ears; the remaining 2 ears, Nos. 770 
and 779, were at first passed for white, but a close examinartion showed 
some seed with a distinct yellow tinge and many with an appreciable 
trace of yellow. An attempt was made to classif\^ ear No. 779, 
which resulted in 368 white seeds and 128 seeds in which a trace of 
yellow could be seen. The classification was, however, more or less 
arbitrary. 

272 



14 HEREDITY OF A MAIZE VARIATION. 

Light-yellow seeds. — From the light-yellow seeds of ear No. 741, 
ten self-pollinated ears were secured. In two of these ears the endo- 
sperm color was obscured by a colored pericarp, and no attempt was 
made to classify the seed, though it could be seen that both yellow 
and white endospenn were represented. Of the eight remaining 
ears, seven showed light-yellow and white seeds m the proportion of 
three yellow to one white. The greatest deviation in any of the seven 
ears was only 2.3 times the probable error, and of the seven ears three 
deviated less and four more than the probable error. The total 
number of seeds from the seven ears was 3,193, of which 812 were 
white, the expected number being 798 ±16.5, a deviation of 14 seeds, 
or 0.85 of the probable error. 

In the remaining ear, No. 815, though also possessed of a light peri- 
carp color, the seeds could be readily classified. The total number of 
seeds in this ear was 388, of which 72, or 18.6 per cent, were white. 
No. 815 was the only ear grown from the light-yellow seed that pro- 
duced yellow seeds as dark as the yellow of the original Gorham 
variety. In the others the color resembled the immediate parent 
seed in intensity. 

Dark-yellow seeds. — From the dark-yellow seeds of ear No. 741, 
thirty-four self-pollinated ears were secured. These were readily 
classified into the following groups: Eleven all-yellow ears of varying 
shades; 18 yellow and white ears, approximating a 3 to 1 ratio; 4 
yellow and white ears, approximating a 15 to 1 ratio; and 1 ear with 
seeds of all shades from white to dark yellow. 

The 18 ears referred to the 3 to 1 ratio are all in close agreement 
with the expected numbers. The total number of seeds for the 18 
ears was 9,004, of which 2,281 were white, a deviation of 29 from 
the expected number, 2,252. There were 11 plus and 6 minus 
deviations. In 8 of the ears the deviation was less than the probable 
error; the widest deviation was 3.7 times the probable error. In 
every ear referred to this group the classes were well marked. In 10 
of the 18 ears, however, the white class contained seeds in which a 
trace of yellow could be made out, but in none was there any evidence 
of discontinuity within the class. 

In the group of four ears referred to the 15 to 1 ratio there was 
also an obvious gap between the dark and light-yellow seeds, though 
the distinction was not as pronounced as m the first group. But 
in these ears it was possible to separate the light seeds mto light 
yellow and pure white with some degree of certainty, and it is this 
class of pure- white seeds that approximates the 6.25 per cent, or 
1 to 15 ratio. The numbers for the four ears referred to this group 
are shown in Table IV. 

272 



PROGENY OF THE ALBINISTIC EAR. 



15 



Table IV. — Number of seeds by seed classes in third xenia generation compared with 

the dihybrid ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 
light- 
yellow 
seeds. 


Nimiber of 
white 
seeds. 


Expected 
number of 

white 

seeds on 

a 15 to 1 

ratio. 


Deviation 

from 

expected 

number of 

white 

seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 

of white 

seeds. 


790 


741 
557 
770 
657 


142 
122 
121 
112 


47 
17 
56 
57 


46±4.4 
35±3.8 
48±4.5 
41±4.2 


+ 1 
-18 
-t- 8 
4-16 


0.2 
4.7 
1.8 
3.8 


6.3 


791 


3.1 


797.; 


7.3 


802 


8.7 






Total 


2,725 


497 


177 


170±8.5 


-f- 7 


.8 


6.5 



In Table V the white and the light-yellow seeds are considered 
as ®ne class contrasted with the dark-j^ellow seeds, and the numbers 
are compared with a 3 to 1 ratio. 

Table V: — Number of seeds by seed classes in third xenia generation compared roith the 

monohybrid ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 

white and 
Ught- 
yellow 
seeds. 


Expected 

number 

on a 3 to 1 

ratio. 


Deviation 

from 
expected 
number of 
white and 

light- 
yellow 

seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 
of white 

and light- 
yellow 
seeds. 


790 


741 
557 
770 
657 


189 
139 
177 
169 


185 ± 7.9 
139± 6.9 
193± 8.1 
164± 7.5 


+ 4 

0.0 
-16 
+ 5 


0.5 

.0 

2.0 

.7 


25.5 


791 


25.0 


797 . . 


23.0 


802 


25.7 






Total 


2,725 


674 


681±15.2 


- 7 


.5 


24.7 







Too much significance should not be attached to the ratios repre- 
sented by the pure-white seeds in these four ears, though the close- 
ness to 6.25 per cent, which is the expected percentage where two 
factors are involved, is suggestive. In nearly every ear the classi- 
fication was more or less arbitrary. Granted that subsequent 
generations show that 6.25 per cent of the seeds fail to produce 
yellow, rather violent assumptions are necessary to account for the 
definite class representing 25 per cent of the total number. It 
would be necessary to assume that the two factors for yellow show 
very different potencies, so that one of them, although received 
from both parents, produces a much lighter yellow than where the 
other factor is received from only one parent. In Mendelian ter- 
minology one of 'the factors, "Y," for example, must be assumed 
to be much less effective than ''Yi", so that the classes yyyiyi, 
Yyy^yi, and YYy^y^ will be either white or very light yellow, while 
all other combinations are dark yeUow. 

Although the 25 per cent ratio is that of a simple Mendelian 
character, it can not be explained as such, since the recessive class 

272 



16 



HEREDITY OF A MAIZE VARIATION. 



may be expected, as iii the previous generation, to produce both 
yellow and white. A less complicated way of looking at these 
results is to admit the incompleteness of segregation, the group of 
25 per cent representing the class in which the character fails to 
come into expression except in an incomplete wa}^. 

PROGENY OF EAR NO. 721. 

The seeds of ear No. 721, the reciprocal of ear No. 741, were in like 
manner classified into white, light yellow, and dark yellow, and each 
planted separately. The results were in general similar to those 
secured from ear No. 741 , except that in none of the ears could the light 
seeds be separated into light yellow and pure white with any degree of 
certainty. ^ 

White seeds. — Five self-pollinated ears were secured from the white 
seeds of ear No. 721. All were pure white. 

Light-yeUow seeds. — From the seeds that were light yellow six self- 
pollinated ears were obtained. Two of these ears would bfe passed for 
pure white except on very close inspection, when a trace of yellow 
could be made out in many of the seeds. No attempt was made to 
classify these ears. The classes in the remaining four ears are shown 
in Tarble VI, where the results are compared with those expected if 
the character was segregating as a monohybrid. 



Table VI. 



-Numher of seeds, by seed classes, in third xenia generation compared with the 
monohybrid ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 
white seeds. 


Expected 
number of 
white seeds 
on a 3 to 1 
ratio. 


Deviation 
from ex- 
pected 
number of 
white seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 

of white 

seeds. 


760 


790 

569 
69 


213 

280 

131 

20 


198±8.2 

146±7.1 

140±6.9 

17±2.4 


+ 51 
+134 
- 9 
+ 3 


1.8 

18.8 

1.3 

1.2 


27.0 


763 


47.9 


764 


23.4 


766 


29.0 







The foregoing classification was that into which the seeds could be 
most naturally divided, though the classes were only moderately well 
marked. In each ear it could be seen that some of the seeds classed 
as white contained minute traces of yellow. No special significance 
should be attached to the large number of white seeds in ear No. 763. 
The classes in this ear were very poorly defined, the gradations in 
color forming almost a continuous series from wliite to dark yellow. 

Dark-yellow seeds. — From the dark-j^ellow seeds of ear No. 721 
15 self-pollinated ears were secured, as follows: 5 with all-yellow seeds 
of varying shades; 4 with yellow and white seeds, approximating a 
3 to 1 ratio; and 6 with seeds of all shadesfrom white to dark yellow. 

The 4 ears which showed classes that were distinctly marked all 
approximated very closely the 3 to 1 ratio. The total number of seeds 

272 



PROGENY OF THE ALBINISTIC EAR. 17 

was 2,644, of which 673 were white, a deviation of only 12 from the 
expected 661 seeds. But in 3 of the 4 ears faint traces of yellow were 
apparent in seeds of the white class. 

Considering the progeny of all the yellow seeds from ears Nos. 741 
and 721 regardless of the intensity of the color, it appears that in 
every ear in which the classes were well marked the white class repre- 
sented approximately 25 per cent of the total number of seeds. 

In many of the ears the seeds classed as white were not pure white, 
and in a few ears these light seeds can be further divided into very 
light yellow and pure white, the latter class representing approximately 
6.25 per cent of the total number of seeds. It will thus be seen that 
while the results from self-pollinating the second-generation plants 
are generally in numerical accord with the Mendelian expectation, 
segregation is apparently incomplpte. 

These results are in striking contrast with the behavior of the 
endosperm texture observed in hybrids between varieties with the 
ordinary endosperm and a Chinese variety with a waxy endosperm. 
In the latter crosses segregation of endosperm texture appeared com- 
plete, but numerical deviations from the expected ratios were of 
common occurrence.^ 

The appearance of classes representing both 6.25 per cent and 25 
per cent of the total number of seeds would be in accord with the 
h}qiothesis that two factors were involved, were it not that both ratios 
occur in the same ear. 

CROSS OF THE ALBINISTIC EAR WITH A WHITE DENT VARIETY. 

It was suggested that the ratios observed in ears Nos. 721 and 741 
of the second generation might be explained on the assumption that 
one of the parents of these reciprocal ears was heterozygous for two 
factors, the other parent possessing but one factor and this in a 
heterozj'gous condition. 

If one of the parents of ears Nos. 721 and 741 was producing yellow 
and white gametes in equal numbere, it was undoubtedly plant No. 47, 
as shown by the results given below. 

FIRST GENERATION. 

Plant No. 47 was used to pollinate 3 ears of A4, a pure-white strain 
continuously pure seeded for three years. If plant No. 47 was pro- 
ducing yellow and wliite gametes in equal numbers these ears should 
have equal numbers of yellow and of white seeds. The results are 
shown in Table VII. (See also fig. 1.) 

I Collins, G. Js., and Kempton, J. H. Inheritance of waxy endosperm in hybrids of Chinese maize. 
Quatri^me Conference Internationale de G6n6tique, Paris, 1912, pp. 347-357. 
272 



18 HEREDITY OF A MAIZE VAEIATION. 

Table VII. — Number of white seeds of first xenia generation compared with a 1 to 1 ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 
white seeds. 


Expected 
number of 
white seeds 
on a 1 to 1 
ratio. 


Deviation 
from ex- 
pected 

number of 
white seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 

of white 

seeds. 


278 


288 
120 
154 


154 
50 
83 


r44±5.7 
60±3.7 

77±4.2 


+10 
-10 
+ 6 


1.8 
2.7 
1 4 


n3.5 


291 


41 6 


632 


63.9 






Total 


562 


287 


281 ±8.0 


+ 6 


.8 


51.1 







These results are thus seen to bear out the assumption that plant 
No. 47 was heterozygous for only one factor. In the next generation, 
however, irregularities occurred. 



SECOND GENERATION. 



Progeny of ear No. 278. — Yellow seeds from ear No. 278 were 
planted in 1911 and 13 self -pollinated ears secured. All showed 
both yeUow and white seeds, and with four exceptions the ratio might 
be referred to the expected 25 per cent. The total number of seeds 
was 4,867. The number expected to be white (one-fourth of the 
total) was 1,217 ±20,3. The actual number of white seeds was 
1,158, a deviation of 59 seeds, 2.9 times the probable error. The 
results are shown in Table VIII. 

Table VIII. — Number of white seeds in the progeny of ear No. 278 compared with the 

monohybrtd ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 
white seeds. 


Expected 
number of 
white seeds 
on a 3 to 1 
ratio. 


Deviation 
from ex- 
pected 
number of 
white seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 

of white 

seeds. 


284 


263 
101 
107 
607 
91 
705 
585 
367 
370 
481 
185 
454 
551 


65 
24 
27 
146 
20 
164 
158 
80 
105 
147 
64 
83 
75 


66± 4.7 
25± 2.9 
26± 3.0 
lo2± 7.2 
23 ± 2.8 
176± 7.7 
146± 7.1 
92± 5.6 
92± 5.6 
120 ± 6.4 
46± 4.0 
114± 6.2 
138± 6.8 


- 1 

- 1 

+ 1 

- 6 

- 3 
-12 
+ 12 
-12 
+ 13 
+ 27 
+ 18 
-31 

-t;3 


0.2 

.3 

.3 

.8 

1.1 

1.6 

1.7 

2.1 

2.3 

4.2 

4.5 

5.0 

9.3 


24.7 


289 


23.8 


716 


25.2 


280 


24.1 


288 


22.0 


279 


23.3 


281 


27.0 


717 


21.8 


286 


28.4 


*285 


30.6 


*287 


34.6 


*283 


18.3 


*282 


13.6 






Total 


4,867 


1,158 


1,217±20.3 


-59 


2.9 


23.8 







* Exception referred to. 

In aU of these ears the number of seeds is large enough to make the 
deviations significant. In ears Nos. 282 and 283 the classes were 
not well marked, but both showed an excess of yellow seeds, and only 
those seeds in which the color was unmistakable were classed as yellow. 
In ears Nos. 285 and 287 the classes were well marked. 

272 



PROGENY OF THE ALBINISTIC EAR. 



n 



Progeny of ear No. 291. — Sixteen self -pollinated ears were secured 
from the yellow seeds of ear No. 291. Again, all showed both yellow 
and white seeds, all but two of which may be referred to the 3 to 1 
ratio. 

The total number of seeds was 8,007. The total number of white 
seeds was 2,012, where 2,002 ±26.1 were expected, a deviation of 10 
seeds. The results are shown in Table IX. 

Table IX. — Number of white seeds in the progeny of ear No. 291 compared with the 

monohybrid ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 
white seeds. 


Expected 
number of 
v/hite seeds 
on a 3 to 1 
ratio. 


Deviation 
from ex- 
pected 
number of 
white seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 

of white 

seeds. 


674 


765 
692 
396 
467 
616 
403 
662 
422 
033 
644 
262 
665 
2o9 
83 
555 
473 


189 
170 

96 
120 
158 

97 
175 

97 
146 
148 

75 
182 

80 

31 
177 

71 


191 ± 8.1 
173± 7.7 

99± 5.8 
117± 6.3 
154 ± 7.3 
101 ± 5.9 
166± 7.5 
105 ± 6.0 
158± 7.3 
161± 7.4 

60± 4.7 
166± 7.5 

67± 4.8 

21± 2.7 
139 ± 6.9 
118± 6.4 


- 2 

- 3 

- 3 

+ 3 
+ 4 

- 4 
+ 9 

- 8 
-12 
-13 

+ 9 
+ 16 
+ 13 
+ 10 

+;is 

-47 


0.2 

.4 

.5 

.5 

.5 

.7 

1.2 

1.3 

1.6 

1.8 

1.9 

2.1 

2.7 

3.7 

5.5 

7.4 


24.7 


675 


24.6 


683 


24.2 


297 


25.7 


294 . 


2.5.6 


295 


24.0 


292 


26.4 


679 


23.0 


678 


23.1 


677 


23.0 


681 


28.6 


293 


27.4 


684 


29.7 


(«5 


37.3 


*676 


31.9 


♦680 


15.0 






Total 


8,007 


2,012 


2,002±26.1 


10 


.4 


25.1 







* Exception referred to. 

In this family, as in the preceding, while the original assumption 
is borne out by most of the ears, the exceptions can not reasonably be 
ascribed to chance. 

In both the variant ears the classes are beautifully distinct, but in 
ear No. G80 some of the white seeds may contam a trace of yellow. 

In ear No. 685 the percentage of white seeds is high, but the 
number of seeds is so small that the de^dation may easily be due to 
chance. 

Progeny of ear No. 632. — Fifteen self-polhnated ears were secured 
from yellow seeds of ear No. 632. Of these all except three ears ap- 
proximated the expected 25 per cent white. The results are shown 
in Table X. The total number of seeds m the 15 ears was 8,661, of 
which 2,014 were white. The expected number of white seeds waa 
2,165 ± 27.2, a deviation of 151 seeds, or 5.6 times the probable error. 

272 



20 



HEREDITY OF A MAIZE VAKIATIOX. 



Table X. — Number of white seeds in the progeny of ear No. 632 compared with the 

monohybrid ratio. 



Ear No. 


Total 

number of 

seeds. 


Number of 
white seeds. 


Expected 
number of 
white seeds 
on a 3 to 1 
ratio. 


Deviation 
from ex- 
pected 
number of 
white seeds. 


Deviation 

divided by 

probable 

error. 


Percentage 

of white 

seeds. 


666 


517 
472 
735 
565 
615 
751 
677 
541 
585 
562 
609 
453 
537 
622 
620 


123 
119 
186 
144 
124 
181 
1.50 
144 
159 
127 
138 
95 
108 
106 
105 


129± 6.6 
118± 6.3 
184± 7.9 
141 ± 6.9 
129± 6.6 
188± 8.0 
144± 7.0 
135 ± 6.8 
146± 7.1 
140 ± 6.9 
152i: 7.2 
113± 6.2 
134± 6.8 
155± 7.3 
155 ± 7.3 


- 1 
+ 1 

+ 2 
+ 3 

- 5 

- 7 
+ 6 
+ 9 
+ 13 

- 13 

- 14 

- 18 

- 26 

- 49 

- 50 


0.2 

.2 

.3 

.4 

.8 

.9 

.9 

1.3 

1.8 

1.9 

1.9 

2.9 

3.8 

6.7 

6.9 


■ 24 8 


656 


25.2 


659 


25 3 


669 


25.5 


665 


24.1 


667 


24 1 


672 


26.0 


658 


26 6 


655 


27.2 


668 


22.6 


671 


22 7 


673 


21.0 


*657 : . 


20 1 


*654 


17.1 


*670 


16 9 






Total 


8,661 


2,014 


2,165±27.2 


-151 


5.6 


23.2 







* Exception referred to. 

Excludmg the 3 ears which do not approximate the 3 to 1 ratio, 
the deviation is only 25 seeds, with a probable error of 24.2. 

The total progeny of the 3 ears, Nos. 278, 291, and 632, consisted of 
44 ears mth 21,535 seeds; of these 5,184 were white. If behaving as 
a simple character we should have expected 5,384 ±43 white seeds. 
Thus there is a deviation of 200 seeds, or 4.7 times the probable error. 
But this deviation results from the behavior of a comparatively few 
aberrant ears and not from a general tendency, or skew, such as was 
found with the inheritance of the endosperm texture.* 

CROSS OF THE ALBINISTIC EAR WITH THE HOPI VARIETY. 

In 1909 pollen from plant No. 47, the same plant that was used as 
the male parent in the crosses referred to in Table I, was used on a 
plant of the Hopi white-seeded variety, producing an ear. No. 44, 
having 249 white and 191 yellow seeds, with the classes very well 
marked. The expected number of white seeds on a 1 to 1 ratio is 
220 ±7.1. There is thus a deviation of 4.1 times the probable error. 
It may be noted that the expected number of seeds on a 7 to 9 ratio 
is 193, but to judge from the behavior of this color elsewhere the 
larger class should have been the yellow mstead of tlie white. 

Three sclfed ears from the yellow seeds of ear No. 44 gave in 1911 
1 poorly developed yellow-and- white ear, 1 ear with 188 white and 
565 yellow seeds, and 1 pure-wMfe ear. 

The appearance of a pure-white self-pollinated ear from a yellow 
seed must be taken as an example of complete reversal of dominance 

' Collins, G. N., and Kempton, J. H. Inheritance of waxy endosperm in hybrids of Chinese maize. 
"Quatrifeme Conference Internationale de G^netiqiie, Paris, 1912. 
272 



DISCUSSION OF BESULTS. 21 

in the parent seed or the complete loss of a Mendelian character, per- 
haps m the same way that endosperm color was lost in the original 
albinistic mutation. With the idea that the alternative characters 
are a function of expression it is to be expected that yellow may again 
appear in the progeny of this ear. The seed for the 1911 experiment 
was planted by the writer, and the classes of the origuial ear are so 
well marked that the chance plaiitmg of a white seed among the 
yellow seeds is very improbable. The progeny of this pure-white ear 
will be carefull}^ watched for the appearance of yellow. The ear is 
well filled and fully matured and the closest scrutiny fails to disclose 
the least trace of yellow endosperm.^ 

DISCUSSIOX OF BESULTS. 

Viewed in a general way it can be said that pure-seed progenies of 
the albinistic ear have resulted in all shades of yellow from the 
merest trace to the fully developed orange of the variety from which 
the mutation originated. The pronounced tendency for the seeds to 
fall mto two groups representing 25 per cent and 75 per cent of the 
total number shows that the inheritance is Mendeloid, though not. 
definitely alternative. The grouping into classes representing 25 per 
cent and 75 per cent suggests that a smgle character mth somewhat 
variable dominance is mvolved, but on this assumption the segrega^ 
tion must be held to be mcomplete, since the recessive class shows 
definite traces of yellow. 

The appearance m some of the ears of a class apparently pure white, 
representing approximately 6.25 per cent, suggests that two factors 
are involved. But if two factors are involved, the definite class 
representing 25 per cent of the seed in the same ears that show the 
pure-white class of 6.25 per cent can be explamed on the factor 
hypothesis only by elaborate and unwarranted assumptions. 

The small class constitutii;ig 6.25 per cent also argues against the 
presence of more than two factors. For if three or more factors are 
involved the same violent assumptions are required to accommodate 
the 6.25 per cent ratio that are required to accommodate the 25 per 
cent ratio with two factors. 

The definiteness with wliich the two classes represent 25 and 75 
per cent is merely an addition to the large mass of evidence already 
on record with respect to a great variety of plants and animals, to 
the effect that alternative characters tend to segregate in equal 
numbers. 

The more significant fact from the theoretical pomt of view is that 
while the segregation is usually numerically exact, it is by no means 

I Since this bulletin was sent forward for publication the 1912 crop has been harvested. Nine self- 
pollinated ears from tiie seed of this pure white ear were secured. Five of these are pure white. All of 
the others have some seeds th^t are unmistakably yellow, though the color is faint. 
272 



22 HEREDITY OF A MAIZE VARIATION. 

complete; that is, the dominant character, yellow endosperm in this 
case, is not completely absent from individuals of the recessive class. 
This is shown not only by the presence of a faint-yellow color in most 
of the seeds, but also by the fact that apparently pure-white seeds 
from an ear in which the classes were well marked may produce seed 
with a fully developed yellow color when self -pollinated. 

The results appear as evidence against the idea of gametic purity 
and alternative inheritance, but are rather in accord with the modifi- 
cations of the Mendelian theory that have been advanced by Castle,^ 
Reid^^ Cook,' and others. These authors, while holding diverse views 
m many particulars, all agree that segregation is incomplete in the 
sense that the extracted dominants and recessives transmit traces 
of the alternative character in more or less latent form. 

The mathematical regularity exliibited in the expression of most 
alternative characters is so striking and attractive that careful com- 
parisons between the original and extracted types are often over- 
looked. There may have been a tendency to assume that if the 
characters segregated in accordance with an expected ratio the segre- 
gates were necessarily pure. The numerous examples where this 
* has now been shown not to be the case should call for a careful re- 
examination of the classes in the various Mendelian experiments with 
this point in mind. That large numbers of individuals bred from 
the extracted types fail to bring the alternative characters into full 
expression can no longer be taken to prove that the types are "pure." 

CONCLUSIONS. 

The present paper is a study of the inheritance of one of the endo- 
sperm characters of maize in the progeny of an albinistic mutation. 
The results are of interest in relation to one of the general prob- 
lems of heredity — the segregation of characters in the offspring of 
hybrids. 

It has been assumed that alternative characters when brought 
together in hybrids will separate and reappear in pure form, un- 
changed by the temporary union. The endosperm characters of 
maize afford excellent material for the study of this question and 
have played an important part in establishing the theory of complete 
segregation. The numerical regularity wdth which many characters 
reappear in the later generations of a hybrid is one of the chief argu- 
ments for the theory of segregation or alternative transmission. 

The results here reported of the inheritance of an albinistic varia- 
tion seem to demonstrate that in this instance, while the original 

» Castle, W. E. The inconstanoy of unit characters. American Naturalist, vol. ■i(\, no. 540, June, 1912, 
p. 351. 

5 Reid, G. A. O'B. The Laws of Iloredity, London, 1910, pp. lo9-ias. 

' Ccok, O. F. Transmission inheritance distinct from expression inheritance. Science, n. s., vol. 25, 
June 7, 1907. 
272 



CONCLUSIONS. 23 

characters reappear, they are not the same; in. other words, the segre- 
gation is not complete. 

Previous experimenters in this field have found the endosperm color 
somewhat refractory as an example of the segregation theory, but by 
subdividing the character mto factors it has been possible to bring 
their results into conformity with the theory. The results here 
reported do not lend themselves to such an explanation. 

The study is based on the progeny of a white ear that appeared in 
a carefully selected yellow variety. The circumstances under which 
the variation appeared, as v/ell as the behavior of the progeny, show 
that the occurrence of tliis white ear can not be ascribed to the acci- 
dental admixture of seed but must have arisen as an abrupt mutative 
change of characters. 

In the original mutation the white color was almost completely 
dominant over the yellow. In subsequent generations, however, 
the yellow reappeared as a dominant character, though variable in 
intensity. The results accord numerically with the Mendelian ex- 
pectation, but the recessive wliite seeds instead of being pure show 
minute traces of yellow. 

Imperfect segregation must be taken into consideration as an obsta- 
cle to securing combinations of characters by hybridizing. The 
occurrence of Mendelian ratios can not be taken as conclusive evi- 
dence that subsequent selection will not be necessary to establish 
the full expression of characters. 

272 



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